These rolling mills have their application, in line, for example, in annealing and pickling lines or, off line, such as reversible rolling mills, for metal strip.
A Quarto rolling mill stand comprises a retaining stand wherein are provided four parallel axis rollers, namely respectively two upper and lower working rollers, defining the gap of the passage of the strip to be rolled, as well as two upper and lower bearing rollers, bearing respectively on the working rollers on the side opposite that of the gap of the passage.
A Sexto rolling mill comprises two additional rollers in relation to a Quarto, namely two intermediate rollers interposed respectively between each working roller and the corresponding bearing roller.
In such rolling mills, each bearing roller and each intermediate roller, are mounted rotatingly at their ends on chocks, by the intermediary of bearings, for example with rollers or hydrostatic bearings. These chocks are supports which can be displaced according to a direction parallel to the clamping plane, between the posts of the stand.
Conventionally, balancing cylinders allow for the displacement of the chocks of the intermediate rollers. These balancing cylinders make it possible to change the relative position of the chocks and of their roller, which makes it possible among other things, to open the stand in order to facilitate the engagement of the product to be rolled, or to displace these elements in order to facilitate the disassembling of the rollers. These balancing cylinders can also make it possible to camber the intermediate rollers.
An advantage of a Sexto rolling mill stand is the possibility of using, in comparison with a Quarto stand, working rollers of smaller diameter, which makes it possible to obtain a reduction in the thickness greater than the product to be rolled, for the same rolling force.
A Sexto rolling mill moreover offers the possibility to axially offset the two intermediate rollers, and for the purpose of applying the rolling force solely on the width of the strip to be rolled, not over the entire length of the working rollers.
In a Sexto rolling mill referred to as “laterally supported”, often, the working rollers are not mounted on chocks, but on the contrary are provided floating. It is then necessary to maintain their axial position, by the intermediary of axial abutments, but also to maintain their lateral position by means of side bearing members, such as side bearing rollers or tracks.
It is as such known from document U.S. Pat. No. 4,531,394 a rolling mill design of the laterally supported Sexto type. Such a rolling mill comprises a retaining stand comprising two pairs of posts separated from each other at the two ends of the stand, at least two posts of the same pair defining an access window. Such a rolling mill comprises two working rollers, two bearing rollers and two intermediate rollers, inserted respectively between one of the working rollers and the corresponding bearing roller.
In this rolling mill, the bearing rollers and the intermediate rollers are mounted rotatingly at their ends on chocks, whereas the working rollers are provided floating. Each working roller is laterally supported, on each side of the working roller, by a side bearing roller, itself bearing on two series of tracks (guiding rollers) arranged over the length of the roller.
In this rolling mill design, for each working roller, the corresponding two side bearing rollers are integral with the two chocks of said intermediate roller. Each side bearing roller, as well as its bearing tracks are mounted on a support arm that extends between the two chocks of the intermediate roller, with each arm being mounted pivoting around a rotating shaft of which the ends are threaded into bores of the chocks and fixed to the latter.
The intermediate roller, chocks of the intermediate roller, support arms (right and left) unit, form a self-supporting unit, commonly referred to as a “cassette” or “insert” which can be introduced into the stand, or removed from the stand through the access window, during maintenance, by sliding the unit according to the direction of the rollers.
In such a rolling mill, four load distributing beams extend respectively between the posts of the stand, respectively on support arms of the upper cassette and of the lower cassette. Each load distributing beam supports a beam, referred to as preloading, mobile in translation in relation to the corresponding load distributing beam, which can be displaced towards the inside of the stand according to a substantially horizontal direction. Pushing cylinders make it possible to constrain the mobile beam in contact with the support arm pivoting to preload the side bearing roller on the working roller.
It is also known from document U.S. Pat. No. 6,041,636 an alternative design for a rolling mill of the laterally supported Sexto type, with “insert” or “cassette”. As in the preceding document, the intermediate roller, chocks of the intermediate roller, support arms (right and left), side bearing rollers and tracks, right and left, unit, form a self-supporting unit which can be introduced into the stand or removed through the access window of the stand during maintenance, by sliding the unit according to the direction of the rollers.
In this document U.S. Pat. No. 6,041,636, the chocks of the intermediate rollers are mounted on camber blocks. The cylinders of the camber blocks make it possible, during operation, to bring the intermediate rollers closer together, in a working position shown in FIG. 5 of this document, or to separate the intermediate rollers to a position, shown in FIG. 4, allowing the inserts to be removed by sliding.
In this document, it is known to supply with lubricant the rollers of the tracks of the support arms of the insert, using a source of lubricant. Connection/disconnection devices make it possible, in the working position of the rollers, to connect the source of lubricant to lubrication bores provided in the shocks, and to automatically disconnect the bores when the intermediate rollers and their chocks are vertically separated by the camber blocks.
No additional operation to connect/disconnect the source of lubricant is required during maintenance, in particular when the inserts must be removed or introduced into the stand. To this effect, each connection device comprises an element, marked 57 named “plunger”, hollow, intended to conduct the lubricant, and which makes it possible, in the working position of the intermediate rollers, such as shown in FIG. 9, to attach in a relatively sealed manner the hole of the chock by the intermediary of a seal. This element is mobile, vertically in translation, constrained towards its sealed position by means of a spring, marked 58. In the connection position, the lubricant flows from the source of lubricant through the mobile element and to the hole of the chock. The lubricant then flows from the bore of the chock, and to the rollers of the bearing tracks mounted on the support arm by the intermediary of the shaft, marked 17 which is hollow and whereon the support arm is mounted pivotingly.
When the intermediate rollers are separated to their position of withdrawal by the camber blocks, the course of travel of the mobile element is limited, less than the course of travel of the displacement of the camber blocks, as such making it possible to guarantee an inter-space between the mobile element and the chock, such as shown in FIG. 8. It is then possible to remove the insert, without friction between the chocks and the mobile element.
In the insert (or cassette) of document U.S. Pat. No. 4,531,394 or of document U.S. Pat. No. 6,041,636, the ends of the shafts marked 17 of the support arms are inserted into bores made in the mass of the body of each chock. These bores also serve as ducts for the lubricant supplying these shafts which are hollow. Furthermore the ends of the intermediate roller are mounted rotatingly on the chocks by the intermediary of bearings received in other bores of the chocks.
When the cassette is mounted, these ends of the shafts of the support arms and of the intermediate roller must be introduced simultaneously into the corresponding bores of the chocks. Likewise, and according to the observations of the inventor, disassembling the cassette requires separating the two chocks by a distance greater than their nominal spacing for mounting, requiring that the intermediate roller and the two support arms be removed simultaneously.
In practice, these operations are delicate and require specific tools comprising a stand making it possible to turn over the lower cassette. Due to the simultaneous exiting of the support arms and of the intermediate roller during the disassembling operations, another specific stand is used in order to provide support for the support arms, the intermediate roller and the chocks during these disassembly/mounting operations.